Stoker



' 1 7. I May 92 c. L. DAVIDSON ISTOKER Filed July 21, 1925 2Sheets-Sheet 1 Patented May 3, 1927.

7 Application filed July 21,

i This invention relates to stokers. The object of the invention is toprovide means to simplify and improve the construction and operation ofstokers to render i the same more certain and efficient.

A further object is to provide means which are simple and eflicient fordrying the fuel and reducing the same to a condition in a which it maybe ignited at its point of de- 10 livery to the stoker grate.

A further object is to provide means f0 passing heated. air from insidethe furnace chamber through the fuel in advance of the delivery of thefuel into the furnace chamber, and in the direction of theline ofpenetration of the ignition of the fuel.

Other objectsof the invention, will appea more fully hereinafter.

The: invention consists substantially inf the construction, combination,location and relative arrangement of parts, all as will be more fullyhereinafter set forth, as shown in the accompanying drawings, andfinally pointed out i-n-the appended claims.

Referring to the accompanying drawings: Figure 1 is a broken view inelevation of the front of a furnace showingthe application thereto of afuel drying and heating arrangement in accordance with the princi- 3o ls of my-invention.

' Fig.1 2 is a view in vertical longitudinal sectionaon the line"2.2,Fig. 1, looking in the'dir-ection of the arrows; i

3 is a detacheddetail View, in perspective of a baremployedin thegrating or 1 grill of the fuel feed-ho'pper. Y Tlie'same part"designated by the same reference numeral wherever 'ito 0 on r sthroughout the several views.

In theeconoinical operation of stokers it yis'frequently desirable toemploy a cheap grade of fuel, such as anthracite coal of buckwheat,.rice or barley size, culm,

' coke braize and othercharacters of fuel, in- -cluding-- bituminousvand semi-bituminous coal, lignites and the like. These fuels frequentlycontain morezorless moisture, some of them running as high as 11% ormore at times. It is common practice to deliver the fuel fromthe furnacefeed hopper upon the chain grate, the fuel spreading fromthe hopper thefull width of the grate tothe desired thickness of bed. On account ofthe moisture present in the fuel it has been found 'diiiicult, in.practice,'to effect ignition of the fuel atuthe point where,or'sufliciently STOKER. I

i923. Serial a; 652,879. I L J CHARLES L. i Avrnson, on NEW YORK, N. Y.

close to point where the fuelyenters furnace chamber, with, the resultthat there is 'a failure to effect complete combustion of the fuel n itstravel through the furnace,

thereby failing to secure the ful-l value and advantage of the fuel inheat' production, and a loss of efliciency. Where the conditions of highratings are desired and variable levels are to heencountered, thelossbfefiiciency from this cause becomes more pro.-

nounced. Various expedients have been proposed to overcome thisdifficulty. Among these expedients special shapes of fire; archeshave'been devised with the idea of hastening the lgnltlQIhOf theincomingfuel by intensifying the heat directly over the pOintbfj Hentryoffthe fuel. This, however, is not suffic ent andhas ,not' provedsatisfactory in securing a sufliciently. rapid and complete ignition atall times, and with all class"es;of fuel; Moreover, where particularlysmallparticles of fuel of high moisture, content are used the airpressure-within the furnace necessary. todrive the heat'down through thefuel bed at thepoint where the fuel isfinally ignited, creates such anintense heat'thfatit frequently. warps or'otherwiseinjures the grates,and, sometimes puts the stoker out of I commission. Where largerparticles'of the fuel are used the thorough. ignition of, the

ent re lumps is slow, even with the, intensified heat causedbya.-special shape of fire arch, with the ,result that complete combustion ofthe fuel; isnot secured. ',Also,, in

the use of special. fire arches the direction I of 1 flow of the airsupply to the f-urnacechamber, o r through the fuel bed; as-wellzasthatof the heated products of combustion -is opposite tothe direction ofignition penetratiojir, This retards theprocess of. ignition,

frequently thelower layers of theffuel failing to ignite, and.wherevariable loads -are-re quired with sudden maximums imposed, the

ignition is not only slow butfit frequently fails. entirely, and in anyevent,.fuel loss results. It has; also been proposed to force, heatedairthrough the fuelbed after it has reached and hasbeen spread over thegrate surface, butin this case a considerabletravel of the fuel throughthe furnace chamberv after entering such chamber takes place beforereaching the point iwhere the hot. air

draft is imposed, or elsethe fuel is-p'assed from one hopper throughapreliminary dry ing and heating chamber, and delivered therefrom intoanother hopper -from which I thereby some of the volatiles of the freshfuel itis spread onto the travelingchain grate of the furnace. In thesecases there is a failure to secure satisfactory results. Inthe firstcase noted, ignitionof the fuel does not take place at the point whereit enters the chamber, and hence there is a retarded ige nition, failureto effect complete combustion during the remaining travel of the fuelthrough the chamber on initial travel'of the fuelthrough; the chamberWithout accomphshing any result,-a'nd a loss of efficiency,

The second instance noted involves the use of an auxiliary hopper andconveyor which adds to thecost, takes up space, and requires additionalcare.

It is among the special purposes of my present invention to providemeans in a stoker which avoids the difficulties noted, and others, andin amost simple, inexpensive and effective manner, and in carrying outmyinventlon I propose to provlde a grating or grill in the front wall ofthe usual fue1 feed hopper which is mounted in the ordif nary manneronthe front wall of the furnace, and at a point near the lower or deliveryend of the said hopper, said grill or rating opening into the lower endof the,

i (r hopper and also into a closed chamber or windbox to which isconnected a pipe or other connection to an air evacuating pump, so as tocreate a draft fromthe interior of the furnace chamber through the fueldelivery end opening ofthe fuel feed hopper and through the body of thefuel in the lower end of the hopper chute. By this means I am enabledtoeffect the thorough tion or combustion of smoke in certain cases,"where, for instance, fuel of a highly volatlle nature is used, bydrawing heated smoke, or other unburned products of the combustion fromthe furnace chamber and passing the same through the incoming freshfuel, as above explained, as well as by extracting before'it enters'thefurnace chamber, and

then returning or passing the same into the furnace chamber beneath thegrate where they pass through the fuel bed and are consumed.

I also'am enabled to effect preliminary heating of the fresh. fuelbefore it enters the furnace chamber, to a degree sufficient to enableignition thereof to take place the instant it enters or even just beforeit enters the furnace chamber, or by the time or before it reaches thegrate. Moreover, the direction oftravel of the heated air and gasesthrough the 'freshfuel is in the direction of ignition'penetration, andsince the entire thickness of stream of incoming fresh fuel is traversedby the hot air and gases efficient ignition is attained quickly and itspenetration through the entire stream of flow of fuel is effectedrapidly and thoroughly. I am therefore enabled to increase the effectivelength of the grate surface without physical extension thereof, and tosecure a more complete combustion of thefuel whatever the sizeof itslumps, and a very high degree of efficiency is attained even under themost exacting conditions of variable loads and ratings.

In the'drawings I have shown a simple illustrative structure embodyingthe principles of my invention wherein 5 designates the usual fuel feedhopper at the front of a furnace, 6 the usual fire arch, 7 the furnacechamber and 8 the usual traveling or chain I grate. These parts may beof the usual or of any desired structure or type, the fuel feed hopperdelivering onto the grate at the point where the fuel and fuel chamber.

In accordance; with my invention I provide the lower'portion of thefront'wall of the hopper, oppositethe open delivery end grate enter the9 of said hopper, with a grating or grill. This can be constructed inany desired manner. I have shown a simple arrangement wherein the lowerportion of the front wall of the hopper is form-ed of a series of bars 9which, in the illustrative arrangement shown, are

provided with'hooked upper ends 10, de-

signed to engageover a supporting rod 11. The lower ends of these barsrests against a rod 12, as shown. Any'other suitable arrangementforsupporting these bars 9 may be employed. The lower portions of thebars are reduced in width, as indicated'at 13, so

as to form spaces, openings or passages 14,

between the edges of adjacent bars when placed in position for use. Inpractice these openings or passages 14, should be approxi- I mately ofthe same area as are the openlngs through the chain'grate. The gratingor grill portion of the fuel feedhopper is enclosed within a closedchamber 15, 'with the chamber 15 may be more-0r less evacuated of air,thereby creating a draft from the interior of the furnace chamberthrough the which is connected a pipe 16, through which open deliveryend of the fuel feed hopper takesplace before the fue1 actually reachesabled to eflectively utilize the entire chain thegrate or enters thefurnace chamber, and hence the fuel is in condition to become ignitedjust before or at the time of its entry into furnace chamber, and thepenetration of the ignition is rapid and complete throughout the entirethickness of the stream of entering fuel. a t

The heated air and gases drawn through the fuel in the manner abovedescribedmay be returned into the furnace chamber at some convenient orany desired point beneath the chain grate surface for furtherutilization, or may be otherwise disposed of, as may be required ordesired.

It will also be observed that I employ no auxiliary feed hopper orconveyor, as I use only the regular and usual feed, hopper which isfurnished as a part of the regular equipment. There is nothing added tothe length of the chain grate and still I am engrate length. I requireno additional preheating chamber through which the fuel is handled. Bycontrolling the degree of vacuum maintained in the wind box 15,1 am

enabled to handle any character of fuel em,

ployed and am able to take care of any desired rang-e of temperature, orto meet any required variations in load. I am also enabled to effect asubstantial reduction of smoke, and to secure a very high degree of fueleconomy and furnace efliciency.

It will also be observed that the operation above described does not inany way interfere with the usual draft, forced or otherwise, under whichthe furnace is operated.

Having now set forth the objects and nature of my invention and aconstruction embodying the principles thereof,yI wish it to beunderstood that many changes'and variations inthe details andarrangement may readily occur to persons skilled in the art, and stillfall within the spirit and scope of wall opposite the furnace entranceand means to pass hot gases from thechamber through said spaces. 1

2. In a stoker, a furnace chamber, a aw, eling grate, and a fuel hoppermounted at the front of the furnace chamber and delivering thereintoonto said grate at itspoint.

of entry, a supporting rod arranged to extend transversely across thefront wall of said hopper, bars supported on said rod and spacedapart'at their edges to form apor tion of said front wall with spacestherebetween, a closed chamber exteriorly enclosmg said bars,and anexhaust pipe connection to said closed chamber;

In testimony whereof I have hereunto'set my hand on this thirteenth dayof July, A. D. 1923. a Y

' CHARLES L. DAVIDSON.

